Dates are struck on coins, not engraved in them.
If you're referring to US cents, the first cent was minted in 1793.
If you're referring to British pennies, that denomination has been used for at least 1000 years so it's not possible to determine the exact date of the first issue.
1909
the date engraved is 1620
The 1909 S VDB wheat cent is the rarest to date.
Wheat cents were made from mid-1909 to the end of 1958.
The oldest British Penny potentially still in circulation would be the 1971 New Penny.
The metal is soft & they are stamped with an engraved die.
This was a post-mint modification of the penny. Any such modification destroys virtually all collector's value. It may not even be accepted in all places of business as legal tender.
The counter stamped date was not done by the US Mint and adds no value at all to the coin. The coin is worth one cent unless you find someone that wants it.
the date of a penny is on the front
1935
A penny wirh a small date on it
1793